Cook bacon in a large Dutch oven over medium heat until crispy. Use a slotted spoon to transfer bacon to a paper towel lined plate.
Cook onions in bacon fat until golde, about 5 minutes. Add garlic and cook about 30 seconds more. Stir in flour and cook until it begins to brown, about 1 minutes. Stir in broth, water, and potatoes. Simmer until potatoes break down and soup has thickened, about 45 minutes.
Beat egg yolks and sour cream together. Whisk 1 c of hot soup into egg mixture, then stir egg mixture back into soup pot. Add herbs and stir constantly over medium low heat until thick and creamy, about 5 minutes. Do not allow soup to come back to a simmer, or eggs and the sour cream will curdle. Stir in bacon and serve.